With such a pressure swing adsorption type of gas production device, the off gas discharged from the adsorption towers contains the purification target gas, and therefore a membrane separation unit is used to separate miscellaneous gases from the off gas, and then the off gas is returned to the source gas supply route as recycle gas, thus improving the purification target gas production efficiency while also reducing the load on the adsorption towers.
In one conventional example of such a pressure swing adsorption type of gas production device, off gas discharged from adsorption towers via an off gas discharge route is guided to a pressure boosting unit (pressure booster), and then after the pressure is boosted by the pressure boosting unit, the off gas is guided to a membrane separation unit (e.g., see Patent Document 1).
Patent Document 1 discloses that the source gas is a hydrogen-containing gas that contains hydrogen as the purification target gas, and contains carbon dioxide and methane as miscellaneous gases.
It should be noted that in the configuration in Patent Document 1, after passing through the membrane separation unit, the hydrogen-containing gas is supplied to a carbon dioxide separating membrane for separating out carbon dioxide, and the resulting hydrogen-containing gas is returned to the source gas supply route as recycle gas.
Note that although not described in detail in Patent Document 1, in order to avoid the case where the pressure boosting unit is negatively affected by operating in an empty operation state where no off gas is present, and in order to reduce the internal pressure in the off gas discharge route in the desorption process, it can be thought that the output rate of the pressure boosting unit is defined such that the amount of off gas discharged from an adsorption tower in each desorption process is equivalent to the amount of output from the pressure boosting unit in the period from when one adsorption tower starts the desorption process until when another adsorption tower starts the desorption process.